DESCRIPTION (adapted from the Abstract): Studies of HIV2-infected individuals have demonstrated a significantly slower progression to AIDS. Most HIV-1 cohort studies have found 5-15% of their participants fit a definition of long-term non-progression, whereas 86-95% of HIV-2 infected individuals would be similarly classified. This dramatic difference in pathogenicity provides a unique opportunity to identify viral and host immune mechanisms involved in closely related and relevant virus system that is predicted to have a significantly slower course of progression. Significant advances in our understanding of HIV pathogenesis have come from studies of primary HIV-1 infection. The Principal Investigator proposes to characterize primary HIV-2 infection as a model system for long-term non-progressive HIV infection. The full spectrum of HIV primary infection will be assessed by recruiting women from a sub-selected high risk population, frequently monitored for early virologic and immunologic evidence of infection, irrespective of clinical symptomatology. By characterizing the cellular immune responses and viral characteristics found in primary HIV-2 infection, the Investigator believe that critical early determinants of HIV pathogenicity may be elucidated. She speculates that the lower pathogenicity of HIV-2 will be reflected in distinct difference sin the cellular immune responses to this virus during primary infection. Such responses would likely lower viral replication during this critical period of infection, resulting in a lowered viral set-point predictive of long progression. The identification of temporal, qualitative, and quantitative aspects of these immune responses should contribute to out growing understanding of the determinants of HIV pathogenicity.